City officials say they're warning about two dangerously strong types of heroin that are thought to be the cause of several recent overdoses, including two that were fatal.

Portland officials are delivering flyers around the city warning of two types of heroin circulating in the area that could be the cause of an unusual number of recent overdoses, including two that were fatal.

City officials say one is a dangerously strong uncut black tar heroin from New York City that's "chucky, sticky and dark brown." Another type, often referred to as "China White," appears to have been cut with prescription drugs, creating a potentially deadly combination.

The drugs came to light after the city sought help from the public in determining the source of dangerously strong heroin that killed two men recently and caused 11 other overdoses.

Spokeswoman Nicole Clegg says Portland Public Health outreach workers will be out on the streets today distributing flyers that alert the public to the risk of overdosing on the drugs.